The present invention relates to a method and apparatus for diagnosing or detecting faults in circuits such as signal processing circuits of a video camera system.
In a digital signal processing circuit of an electronic apparatus or system, such as a digital video camera system, an analog image-sensed signal obtained from a charge-coupled device (CCD) image sensor or the like may be converted into digitized form and subjected to a number of non-linear signal processes so as to generate a video signal. More specifically, in such digital video camera system, image-sensed light obtained from a subject by color image-sensing units (such as CCD image sensors or the like) may be decomposed or separated into three primary color light components, that is, a red (R) light component, a green (G) light component, and a blue (B) light component. The three primary color image-sensed signals may be converted into digital image-sensed data by an analog-to-digital (A/D) converter and supplied to a pre-process circuit, wherein pixel imperfection compensation, pixel shading compensation, and so forth may be performed. Thereafter, the three primary color image-sensed data signals may be supplied to a process circuit, wherein linear matrix processing, gamma correction, knee correction, aperture correction or the like may be performed. Such process circuit may produce brightness or luminance data and color-difference data from the processed three primary color image-sensed data signals. Such luminance data and color-difference data may be converted into analog luminance and color-difference signals by a digital-to-analog (D/A) converter. Thereafter, a composite video signal may be generated by an encoder based on such luminance signal and color-difference signal and supplied therefrom. Further, the luminance data and the color-difference data may be supplied to a rate converter circuit wherein, for example, a clock rate may be converted into a clock rate corresponding to a video tape recorder electrically connected to the video camera system. The signal having a converted rate may be recorded in the video tape recorder.
Processing operations of the pre-process circuit, the process circuit, and the rate converter circuit may be changed by varying parameters or parameter data of such circuits. As such, parameter data may be supplied to and held in the respective circuits prior to the initiation of the desired operations.
In the above-described video camera system, the pre-process circuit, the process circuit, and the rate converter circuit or the like may be respectively formed as integrated circuits. These integrated circuits may be installed on one or more printed circuit boards by a number of techniques, such as soldering. To ensure that such integrated circuits are properly installed and/or properly coupled together, such installation and coupling may be checked or confirmed. However, upon detection of a failure, the location or cause of such failure may be difficult to determined. That is, each component or integrated circuit (or its associated solder joints) along with the connections therebetween may need to be checked. Since the components or integrated circuits may be densely packaged and since the signals are processed in digitized form, it may be difficult to locate the faulty spot or spots. As a result, the time and cost to locate and repair a fault may be relatively large.